The following abbreviations and terms are herewith defined:
3GPPthird generation partnership projectACK/NACKacknowledged/not acknowledgedAIacquisition indicatorAICHacquisition indicator channelBCCHbroadcast control channelCQIchannel quality indicatorDPCCHdedicated physical control channelDPCHdedicated physical channelDPDCHdedicated physical data channelDLdownlink (e.g., node B to UE)E-DCHenhanced dedicated physical channelE-DPDCHenhanced dedicated physical data channelE-DPCCHenhanced dedicated physical control channelE-HICHenhanced HICH (also known as E-DCH HARQ AIchannel)E-node Benhanced node B (of an LTE system)E-UTRANenhanced UTRAN, also known as 3.9G or LTEF-DPCHfractional dedicated physical channelHICHhybrid automatic repeat request indicatorchannelHSUPAhigh speed uplink packet accessL1layer 1 (control signalling layer)LTElong term evolution of 3GPPNode Bbase station (e.g., node B)OFDMorthogonal frequency division multiplexPRACHphysical (or packet) random access channelRACHrandom access channelSIBsystem information block (also termedmaster information block)UEuser equipment (e.g., mobileequipment/station)ULuplink (e.g., UE to node B)UMTSuniversal mobile telecommunications systemUTRANUMTS terrestrial radio access network
A communication device can be understood as a device provided with appropriate communication and control capabilities for enabling use thereof for communication with others parties. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on. A communication device typically enables a user of the device to receive and transmit communication via a communication system and can thus be used for accessing various applications.
A communication system is a facility which facilitates the communication between two or more entities such as the communication devices, network entities and other nodes. A communication system may be provided by one more interconnect networks. One or more gateway nodes may be provided for interconnecting various networks of the system. For example, a gateway node is typically provided between an access network and other communication networks, for example a core network and/or a data network.
An appropriate access system allows the communication device to access to the wider communication system. An access to the wider communications system may be provided by means of a fixed line or wireless communication interface, or a combination of these. Communication systems providing wireless access typically enable at least some mobility for the users thereof. Examples of these include wireless communications systems where the access is provided by means of an arrangement of cellular access networks. Other examples of wireless access technologies include different wireless local area networks (WLANs) and satellite based communication systems.
A wireless access system typically operates in accordance with a wireless standard and/or with a set of specifications which set out what the various elements of the system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely user equipment, is provided with a circuit switched bearer or a packet switched bearer, or both. Communication protocols and/or parameters which should be used for the connection are also typically defined. For example, the manner in which communication should be implemented between the user equipment and the elements of the networks and their functions and responsibilities are typically defined by a predefined communication protocol.
In the cellular systems a network entity in the form of a base station provides a node for communication with mobile devices in one or more access entities, otherwise known as cells or sectors. It is noted that in certain systems a base station is called ‘Node B’.
Typically the operation of a base station apparatus and other apparatus of an access system required for the communication is controlled by a particular control entity. The control entity is typically interconnected with other control entities of the particular communication network. For example, a radio network controller (RNC) provides control functions in Universal Terrestrial Radio Access Networks (UTRAN) and a base station controller (BSC) provides control functions in GSM (Global System for Mobile) EDGE (Enhanced Data for GSM Evolution) Radio Access Networks (GERAN).
The enhanced dedicated channel has been proposed in the third generation specifications—3GPP (third generation partnership project.
3GPP is standardizing the long-term evolution (LTE) of the radio-access technology which aims to achieve reduced latency, higher user data rates, improved system capacity and coverage, and reduced cost for the operator. The current understanding of LTE relevant to these teachings may be seen at 3GPP TR 25.214 (v4.6.0, 2003-03) entitled PHYSICAL LAYER PROCEDURES (FDD) and herein incorporated by reference. Both frequency division duplex FDD and time division duplex TDD multiple access schemes are considered in LTE. The description in background and the below examples of implementations of the invention are in the context of LTE, though LTE is not a limitation to the environment in which embodiments of the invention may be deployed.
In LTE, an uplink access channel, broadly referred to herein as the RACH, is one typically utilized by the UE for initial access signaling to a network in instances when no dedicated or shared physical channel connection is currently established. For example, the RACH can be used for initial cell access after the UE powers-on. The RACH can be used to perform a location update after the UE moves from one location to another or for initiating a call or for user data transmission. 3GPP specifies that the UE transmit on the RACH a series of access preambles each with increasing transmit power for each access preamble attempt. Each of the access attempts is separated by an appropriate waiting time of sufficient duration to allow detection of an acknowledgment indication (AI) signal from the receiving station Node B. The node B sends the AI on the AICH, and it may indicate ACK, NACK, or no response. There are certain automatic repeat request ARQ procedures that may be followed if the UE does not receive a response to its RACH preamble. Such ARQ procedures are further described for example at co-owned U.S. Pat. No. 6,917,602, issued on Jul. 12, 2005 and entitled “System and Method for Random Access Channel Capture with Automatic Retransmission Request”.
Early development of LTE [3GPP Release 99 specifications (e.g., 25.211-25.215 of Release 99 or Release 4)], considered that once the AI signal was received the UE sent its message on an uplink common packet channel (CPCH), which was seen as an extension of the RACH. Aspects of how the CPCH might have been implemented are detailed, for example, at U.S. Pat. Nos. 6,169,759; 6,301,286; 6,606,341; 6,717,975; and particularly relevant to the RACH at U.S. Pat. Nos. 6,507,601 and 6,643,318. The CPCH was not implemented and it was removed from 3GPP Release 5 specifications. The CPCH did not include certain L1 enhancements since those solutions were included to the uplink only with HSUPA in Release 6. Those L1 enhancements include fast L1 retransmission, hybrid ARQ, and fast capacity allocations. Allocation of a bit rate on the CPCH was fixed, like on the RACH. The CPCH concept introduced a channel allocation scheme which was based on some level of signature combinations, but dynamic assigning of a dedicated resource was rather limited. As noted in U.S. Pat. No. 6,917,602, another procedure was that once the UE receives the AI signal, the UE was allowed to transmit its message on the RACH and the random access procedure would then terminate.
Usage of an enhanced dedicated channel (E-DCH) as random access channel (RACH) shared channel has been described in U.S. patent application No. 60/848,106 and collision detection for random access procedure has been described in U.S. patent application No. 60/897,328. These aim to create a base for high speed and high data rate random access, hereinafter called High Speed Random Access Channel (HS-RACH). There are ongoing investigations as to which techniques of high speed uplink packet access (HSUPA), such as fast inner loop power control, varying bit rate, Node B scheduling with grants, fast acknowledgment/negative acknowledgment (ACK/NACK) for downlink (DL) transmission can be used already in the random access phase. HSUPA is sometimes referred to Enhanced uplink EUL.
The HS-RACH concept has been disclosed in WO2008038124.
The HS-RACH concept has been decomposed in several steps or phases, which are outlined below and illustrated in FIG. 1
(1) Determination of uplink (UL) interference level for open loop power control;
(2) Release99 random access procedure with power ramp-up using specific HS-RACH access slots and signatures indicated in system information block (SIB);
(3) Access Grant and Resource Assignment;
(4) Start of inner loop power control in UL, e.g. on dedicated physical control channel (DPCCH);
(5) Start of inner loop power control in DL, e.g. on fractional dedicated physical control channel (F-DPCH);
(6) Start of UL data transmission, e.g. on E-DCH dedicated physical data channel (E-DPDCH)/E-DCH dedicated physical control channel (E-DPCCH);
(7) subsequent Resource Assignment (update of existing resource assignment) and collision detection and resolution
(8) ACK/NACK of UL data, e.g. on E-DCH hybrid automatic repeat request (HARQ) acknowledgment indicator channel (E-HICH);
(9) ACK/NACK of DL data and channel quality indication (CQI) for link adaptation, e.g. on high speed dedicated physical control channel (HS-DPCCH);
(10) Mechanisms at end of data transmission, end of HS-RACH resource allocation period, collision detection, etc.
In PCT patent application no. WO2008038124, is described how the fast E-DCH allocation could be made possible after the random access preamble procedure is completed. This proposes that AICH (acquisition indication channel) could be used for E-DCH resource allocation.
However, the mechanism to allocate resources to the UE to enable it to use E-DCH is not specified. The mechanism for fast resource assignment, is open. How to fast and efficiently assign resources to UE to start E-DCH transmission from scratch without high collision probability, false alarm and miss detection is an open question.
In UMTS REL 99 to REL7, up to 16 packet random access channel (PRACH) signature sequences can be used in each random access channel (RACH) sub-frame for each RACH defined for the cell. The PRACH signature sequences (preambles) that UEs are permitted to use are broadcast as part of the system information. Not all sequences need to be made available and subdivision of signatures between UE classes is possible. The UE randomly selects one of the PRACH signature sequences applicable to it each time it transmits a PRACH preamble. Each time after having sent the PRACH preamble, it monitors the associated AICH (acquisition indication channel). 16 AICH signature patterns are returned on the AICH. There is a one-to-one mapping between the 16 possible PRACH signature sequences and the 16 AICH signature patterns. The UE checks the AICH for the AICH signature pattern associated with the PRACH signature sequence, that it used in the PRACH preamble. The AICH signature sequence is either coded with “0” (no response), “1” (ACK) or “−1” NACK. If the Node B fails to detect a PRACH preamble a “0” (no response) is indicated, if the Node B detects the preamble and grants permission to transmit the RACH message part a “1” (ACK) is indicated; and if the Node B detects the preamble, but refuses permission to transmit the message part, a “1” (NACK) is indicated. The resource that is used to transmit the message part is defined partly by the standards and partly by system information—broadcast control channel (BCCH). This proposal only supports direct one-to-one mapping.
Currently, the existing AICH cannot be used for a dynamic E-DCH resource allocation. This is because the existing AICH cannot be used dynamically. If one-to-one mapping (PRACH preamble—E-DCH resource mapping) were used, the Node B does not have any means to allocate a specific E-DCH resource because UE selects randomly PRACH preamble. So, no dynamic E-DCH resource allocation can be provided with basic AICH (one-to-one mapping). In other words, a randomly selected PRACH preamble would select the used E-DCH resource in one-to-one mapping and this specific resource may be already occupied by some other UE.